1 /* 2 * Copyright (C) 2009 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.primitives; 18 19 import java.util.Comparator; 20 21 import static com.google.common.base.Preconditions.checkArgument; 22 import static com.google.common.base.Preconditions.checkNotNull; 23 24 /** 25 * Static utility methods pertaining to {@code byte} primitives that interpret 26 * values as <i>unsigned</i> (that is, any negative value {@code b} is treated 27 * as the positive value {@code 256 + b}). The corresponding methods that treat 28 * the values as signed are found in {@link SignedBytes}, and the methods for 29 * which signedness is not an issue are in {@link Bytes}. 30 * 31 * @author Kevin Bourrillion 32 * @since 2009.09.15 <b>tentative</b> 33 */ 34 public final class UnsignedBytes { UnsignedBytes()35 private UnsignedBytes() {} 36 37 /** 38 * Returns the {@code byte} value that, when treated as unsigned, is equal to 39 * {@code value}, if possible. 40 * 41 * @param value a value between 0 and 255 inclusive 42 * @return the {@code byte} value that, when treated as unsigned, equals 43 * {@code value} 44 * @throws IllegalArgumentException if {@code value} is negative or greater 45 * than 255 46 */ checkedCast(long value)47 public static byte checkedCast(long value) { 48 checkArgument(value >> 8 == 0, "out of range: %s", value); 49 return (byte) value; 50 } 51 52 /** 53 * Returns the {@code byte} value that, when treated as unsigned, is nearest 54 * in value to {@code value}. 55 * 56 * @param value any {@code long} value 57 * @return {@code (byte) 255} if {@code value >= 255}, {@code (byte) 0} if 58 * {@code value <= 0}, and {@code value} cast to {@code byte} otherwise 59 */ saturatedCast(long value)60 public static byte saturatedCast(long value) { 61 if (value > 255) { 62 return (byte) 255; // -1 63 } 64 if (value < 0) { 65 return (byte) 0; 66 } 67 return (byte) value; 68 } 69 70 /** 71 * Compares the two specified {@code byte} values, treating them as unsigned 72 * values between 0 and 255 inclusive. For example, {@code (byte) -127} is 73 * considered greater than {@code (byte) 127} because it is seen as having 74 * the value of positive {@code 129}. 75 * 76 * @param a the first {@code byte} to compare 77 * @param b the second {@code byte} to compare 78 * @return a negative value if {@code a} is less than {@code b}; a positive 79 * value if {@code a} is greater than {@code b}; or zero if they are equal 80 */ compare(byte a, byte b)81 public static int compare(byte a, byte b) { 82 return (a & 0xFF) - (b & 0xFF); 83 } 84 85 /** 86 * Returns the least value present in {@code array}. 87 * 88 * @param array a <i>nonempty</i> array of {@code byte} values 89 * @return the value present in {@code array} that is less than or equal to 90 * every other value in the array 91 * @throws IllegalArgumentException if {@code array} is empty 92 */ min(byte... array)93 public static byte min(byte... array) { 94 checkArgument(array.length > 0); 95 int min = array[0] & 0xFF; 96 for (int i = 1; i < array.length; i++) { 97 int next = array[i] & 0xFF; 98 if (next < min) { 99 min = next; 100 } 101 } 102 return (byte) min; 103 } 104 105 /** 106 * Returns the greatest value present in {@code array}. 107 * 108 * @param array a <i>nonempty</i> array of {@code byte} values 109 * @return the value present in {@code array} that is greater than or equal 110 * to every other value in the array 111 * @throws IllegalArgumentException if {@code array} is empty 112 */ max(byte... array)113 public static byte max(byte... array) { 114 checkArgument(array.length > 0); 115 int max = array[0] & 0xFF; 116 for (int i = 1; i < array.length; i++) { 117 int next = array[i] & 0xFF; 118 if (next > max) { 119 max = next; 120 } 121 } 122 return (byte) max; 123 } 124 125 /** 126 * Returns a string containing the supplied {@code byte} values separated by 127 * {@code separator}. For example, {@code join(":", (byte) 1, (byte) 2, 128 * (byte) 255)} returns the string {@code "1:2:255"}. 129 * 130 * @param separator the text that should appear between consecutive values in 131 * the resulting string (but not at the start or end) 132 * @param array an array of {@code byte} values, possibly empty 133 */ join(String separator, byte... array)134 public static String join(String separator, byte... array) { 135 checkNotNull(separator); 136 if (array.length == 0) { 137 return ""; 138 } 139 140 // For pre-sizing a builder, just get the right order of magnitude 141 StringBuilder builder = new StringBuilder(array.length * 5); 142 builder.append(array[0] & 0xFF); 143 for (int i = 1; i < array.length; i++) { 144 builder.append(separator).append(array[i] & 0xFF); 145 } 146 return builder.toString(); 147 } 148 149 /** 150 * Returns a comparator that compares two {@code byte} arrays 151 * lexicographically. That is, it compares, using {@link 152 * #compare(byte, byte)}), the first pair of values that follow any common 153 * prefix, or when one array is a prefix of the other, treats the shorter 154 * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x7F] < 155 * [0x01, 0x80] < [0x02]}. Values are treated as unsigned. 156 * 157 * <p>The returned comparator is inconsistent with {@link 158 * Object#equals(Object)} (since arrays support only identity equality), but 159 * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}. 160 * 161 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> 162 * Lexicographical order</a> article at Wikipedia 163 * @since 2010.01.04 <b>tentative</b> 164 */ lexicographicalComparator()165 public static Comparator<byte[]> lexicographicalComparator() { 166 return LexicographicalComparator.INSTANCE; 167 } 168 169 private enum LexicographicalComparator implements Comparator<byte[]> { 170 INSTANCE; 171 compare(byte[] left, byte[] right)172 public int compare(byte[] left, byte[] right) { 173 int minLength = Math.min(left.length, right.length); 174 for (int i = 0; i < minLength; i++) { 175 int result = UnsignedBytes.compare(left[i], right[i]); 176 if (result != 0) { 177 return result; 178 } 179 } 180 return left.length - right.length; 181 } 182 } 183 } 184